The present invention relates to an exhaust gas recirculation (EGR) system for a turbomachine, and more particularly to a system for purging the exhaust gas from the EGR.
There is a growing concern over the long-term effects of Nitrogen Oxides (hereinafter NOx), Carbon Dioxide (hereinafter “CO2”) and Sulfur Oxides (SOx) emissions on the environment. The allowable levels of those emissions that may be emitted by a turbomachine, such as a gas turbine, are heavily regulated. Operators of turbomachines desire methods of reducing the levels of NOx, CO2, and SOx emitted.
Significant amounts of condensable vapors exist in the exhaust gas stream. These vapors usually contain a variety of constituents such as water, organic and inorganic acids, aldehydes, hydrocarbons, sulfur oxides, and chlorine compounds. Left untreated, these constituents will accelerate corrosion and fouling of the internal components if allowed to enter the gas turbine.
Exhaust gas recirculation (EGR) generally involves recirculating a portion of the exhaust through an inlet portion of the turbomachine where it is mixed with the incoming airflow prior to combustion. This process facilitates the removal and sequestration of concentrated CO2, and also reduces NOx emissions.
Access to the EGR system components may be necessary for maintenance, inspection, repair, or other purposes. The exhaust should be purged from the EGR system: prior to access; when the EGR system is not in use; or when the turbomachine is not generating exhaust. Furthermore, remnants of the exhaust that are not purged may condense within the EGR system leading to the corrosion of the components.
The costs associated with purging an EGR system typically vary with the type of EGR purge system used.
For the foregoing reasons, there is a need for a system and method for purging an EGR system. After use, the system should allow for access to the components of the ER system, and reduce the possibility of corrosion of the components. The EGR system should have few components and provide for a cost effective operation.